?la_syrcond

Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

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ID 766686

Date 4/28/2026

Version

Public

?la_syrcond

Estimates the Skeel condition number for a symmetric indefinite matrix.

Syntax

call sla_syrcond ( uplo , n , a , lda , af , ldaf , ipiv , cmode , c , info , work , iwork )

call dla_syrcond ( uplo , n , a , lda , af , ldaf , ipiv , cmode , c , info , work , iwork )

Include Files

mkl.fi

Description

The function estimates the Skeel condition number of

op(A) * op2(C)

where

the cmode parameter determines op2 as follows:

`cmode` Value	op2(C)
1	`C`
0	`I`
-1	`inv(C)`

The Skeel condition number

cond(A) = norminf(|inv(A)||A|)

is computed by computing scaling factors R such that

diag(R)*A*op2(C)

is row equilibrated and by computing the standard infinity-norm condition number.

Input Parameters

uplo

CHARACTER*1 . Must be ‘U’ or ‘L’ .

Specifies the triangle of A to store:

If uplo = 'U' , the upper triangle of A is stored,

If uplo = 'L' , the lower triangle of A is stored.

n

INTEGER . The number of linear equations, that is, the order of the matrix A ; n ≥ 0.

a , af, c, work

REAL for sla_syrcond

DOUBLE PRECISION for dla_syrcond

Arrays:

ab ( lda ,*) contains the n -by- n matrix A .

af ( ldaf ,*) contains the The block diagonal matrix D and the multipliers used to obtain the factor L or U as computed by ?sytrf .

The second dimension of a and af must be at least max(1, n) .

c , DIMENSION n . The vector C in the formula op(A) * op2(C) .

work is a workspace array of DIMENSION (3* n ).

lda

INTEGER . The leading dimension of the array ab . lda ≥ max(1,n) .

ldaf

INTEGER . The leading dimension of af . ldaf ≥ max(1,n) .

ipiv

INTEGER .

Array with DIMENSION n . Details of the interchanges and the block structure of D as determined by ?sytrf .

cmode

INTEGER . Determines op2(C) in the formula op(A) * op2(C) as follows:

If cmode = 1 , op2(C) = C .

If cmode = 0 , op2(C) = I .

If cmode = -1 , op2(C) = inv(C) .

iwork

INTEGER . Workspace array with DIMENSION n .

Output Parameters

info

INTEGER .

If info = 0, the execution is successful.
If i > 0, the i -th parameter is invalid.

NOTE:

?sytrf

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Developer Reference for Intel® oneAPI Math Kernel Library for Fortran

?la_syrcond

Syntax

Include Files

Description

Input Parameters

Output Parameters